Sodium Monofluorophosphate Research Articles

Oral Fluoride Retention after Use of Fluoride Dentifrices

Fluoride is the only extensively clinically proven means of reducing dental caries. Despite a large body of epidemiological data on the effectiveness of fluoride, delivered in the form of dentifrices, mouthrinses, drinking water, etc., the precise mode of action of fluoride is not completely understood. The purpose of this paper is to report an investigation of the link between oral fluoride levels and applied fluoride dose from dentifrices. Human salivary fluoride clearance studies and equilibrium baseline studies of fluoride in saliva and plaque have been carried out with dentifrices which contained 1,000, 1,500 and 2,500 micrograms fluoride per gram as sodium monofluorophosphate. After a single brushing with a fluoride dentifrice, salivary fluoride decreased in two distinct phases: an initial rapid phase which lasted for 40-80 min, depending on the individual, and a second slow phase lasting for several hours. The latter phase is believed to be due to fluoride released from an oral fluoride reservoir. During regular repeated use of the test dentifrices, the equilibrium baseline fluoride concentration, attained in both saliva and plaque between one application and the next, increased significantly compared with placebo values. Such elevated baseline fluoride concentrations also increased with increasing Na2FPO3 content of the dentifrices. The present work supports the concept that labile fluoride, stored in an oral fluoride reservoir at the time of treatment application, may maintain a prolonged protective effect against dental caries.

Fluoride, Calcium and Inorganic Phosphorus Concentrations in Approximal Plaque Collected from Young Adults 1 and 24 h after Toothbrushing with Fluoride Toothpastes

A within-subject double-blind cross-over study was carried out to examine whether the chemical composition of approximal plaque was altered 1 and 24 h after brushing with fluoride toothpaste. Three fluoride toothpastes were tested, containing either sodium monofluorophosphate with calcium glycerophosphate supplement and calcium carbonate abrasive, a combination of sodium monofluorophosphate and sodium fluoride with the same supplement and abrasive or sodium fluoride with a silica abrasive. A fluoride-free toothpaste with a silica abrasive acted as the control. 19 subjects used the toothpastes separately in randomised order for 1 week each prior to collection of plaque. Contralateral half-mouth approximal plaque samples were collected 1 and 24 h after the last use of each toothpaste. Fluoride, calcium and inorganic phosphorus concentrations of plaque were estimated. The results indicated that brushing with toothpastes containing fluoride and/or calcium supplements resulted in increased concentrations of these constituents in approximal plaque 1 h after brushing. These elevated levels of inorganic ions were not observed in the samples collected 24 h after brushing. It was concluded that the potentially beneficial effect of a raised concentration of fluoride and calcium in approximal plaque observed soon after brushing is lost during the following 24 h.

Reaction characteristics of hydroxyapatite with F? and PO3F2? ions. Chemical states of fluorine in hydroxyapatite

The reactions of F– and PO3F2– ions with hydroxyapatite (HAP) are of interest owing to their dental application. The mechanism of the anti-caries effect of the fluorides, however, is still not clearly understood. In the present study the reaction characteristics of HAP with sodium fluoride (NaF) and sodium monofluorophosphate (Na2PO3F) in aqueous solutions have been investigated using various techniques. F– ions were more easily taken up by HAP than were PO3F2– ions, but no significant change in the X-ray diffraction pattern was observed, though CaF2 was formed only in acidic solutions. X-Ray photoelectron spectroscopy studies have shown that F– ions were ion-exchanged for structural OH– ions of HAP to produce fluorapatite in neutral solution at an F– concentration of 1000–10000 ppm, and that PO3F2– ions were chemisorbed onto the HAP surface or ion-exchanged for HPO2–4 ions. The PO3F2– ions were then partially hydrolysed to free F– and orthophosphate ions, and this was followed by incorporation of F– into HAP. Na+ ions were not incorporated into HAP in contrast to the divalent cations such as Sn2+ and Zn2+ ions reported previously.

Caries-Preventive Effect of Dentifrices Containing Various Types and Concentrations of Fluorides and Sugar Alcohols

The caries-inhibiting effect of unsupervised daily use of four different toothpastes was compared in a 3-year clinical and microbiological study: (1) 0.8% sodium monofluorophosphate (MFP) with 3% xylitol and 6% sorbitol; (2) 0.03% sodium fluoride with 3% xylitol and 6% sorbitol; (3) 0.8% MFP with 9% sorbitol, and (4) 0.03% sodium fluoride with 9% sorbitol. In all 284 children, 12-13 years old at baseline, took part in the study. After 3 years, no statistically significant differences were found between the different toothpaste groups concerning either development of initial or gross caries lesions or number of mutans streptococci and lactobacilli in saliva. However, children with no detectable approximal caries at baseline, who used the MFP toothpaste with the xylitol-sorbitol mixture, showed a lower (p less than 0.05) caries increment as compared with children who used the MFP toothpaste with sorbitol alone.

Effect of Mouthrinsing after Toothbrushing with a Fluoride Dentifrice on Human Salivary Fluoride Levels

In a recent clinical trial of sodium monofluorophosphate dentifrices, oral rinsing habits were found to influence dental caries. Thus an oral fluoride clearance study has been undertaken which was designed to test a possible mechanism for the observed effects. Eight subjects brushed with one of the trial dentifrices and then rinsed using 1 of 8 procedures of varying thoroughness. The salivary fluoride concentration measured 5 min after dentifrice application decreased significantly with increasing rinse volume, rinse duration, and rinse frequency (p less than 0.01, analysis of variance). The area under the clearance curve determined over a further 3 h was significantly higher (300%; p less than 0.01) following use of the least thorough rinsing procedure (5 ml x 2 s once) as compared with the corresponding area under the clearance curve following the most thorough procedure (20 ml x 10 s twice). These findings indicate that rinsing habits may play an important role in the oral retention of fluoride from dentifrices which may, in turn, affect their clinical efficacy.

Journal of Bone and Mineral Research

We report clinical and bone morphometric findings in 18 osteoporotic patients who experienced stress fractures during fluoride therapy. Patients were treated with either sodium fluoride (n = 15), or sodium monofluorophosphate (n = 3). Oral calcium supplementation was given in 11 patients, and vitamin D in 13. Stress fractures occurred after 17.1 +/- 10.3 months of therapy (range: 5-41 months). Atraumatic sudden pain in a lower limb bone extremity, normal initial roentgenogram, high 99technetium uptake on early bone scan, and a 3 to 4 week delay in linear bone condensation area at the same site were characteristics of stress fracture. The most frequent sites were the tibial metaphysis (n = 13), femoral neck (n = 10), and calcaneus (n = 4). Biochemical data showed increased plasma alkaline phosphatase levels in 11 patients, and mild renal failure in 2. Bone histomorphometry was performed on an iliac crest specimen in 10 patients at the time of the stress fracture. Trabecular bone volume was normal, and formation parameters were increased. Features of osteomalacia were encountered in only 2 patients with decreased renal function. Trabecular resorption was increased, as assessed by the osteoclastic surface (1.01 +/- 1.15% bone surface), and the number of osteoclasts (0.44 +/- 0.49 per mm2 bone section). The clinical course was favorable in all patients who stopped fluoride, although 5 patients who continued the treatment had either completion of femoral neck stress fractures to hip fractures (n = 2), or recurrent stress fractures (n = 2), or both (n = 1). Fluoride appears to be a key factor in the pathogenesis of stress fractures, and may be associated with increased trabecular resorption in some treated patients.

Estimation of Fluoride Absorption from Swallowed Fluoride Toothpastes

Eight adults ingested five different toothpastes with and without 1,000 ppm (1 microgram/g) fluoride added as NaF or Na2PO3F. The systemic fluoride absorption was estimated by by comparing the areas under salivary fluoride concentration curves produced after the toothpaste ingestion. Of the toothpastes investigated--chalk, dicalcium phosphate dihydrate, silica or alumina with sodium monofluorophosphate, and silica with sodium fluoride--the fluoride absorption was found to be statistically significantly lower only from the dicalcium phosphate dihydrate toothpaste. Measuring changing fluoride levels in saliva appears to be an acceptable non-invasive technique for following systemic fluoride absorption.

Effect of Monofluorophosphate on Calcium Phosphate Formation in Supersaturated Solutions

The effect of purified monofluorophosphate (MFP) on the formation of hydroxyapatite (HA) in supersaturated calcium phosphate solutions was determined. In solutions initially at pH 7.4 and seeded with HA crystals, MFP was hydrolysed to a small extent, releasing F-. Once the crystal growth-enhancing property of this F- was compensated for, 4 mmol/l MFP could be shown to inhibit precipitation by 40%. Without compensation for F-, MFP appeared to inhibit precipitation by only 18%. This inhibition was weaker than that caused by pyrophosphate or ethane-1-hydroxy-1,1-diphosphonic acid. Because MFP is hydrolysed on apatite surfaces to F-, use of sodium MFP as an anticaries agent is unlikely to cause significant inhibition of enamel remineralization.

Effect of a desensitizing dentifrice on dentinal hypersensitivity

The objective of this study was to assess the effectiveness of a dentifrice with 2% dibasic sodium citrate in poloxamer 407 in decreasing dentinal hypersensitivity. The test toothpaste was compared with a control toothpaste containing 0.76% sodium monofluorophosphate in a 6-week double-blind clinical trial. A total of 75 hypersensitive teeth were examined in the test group, while 100 hypersensitive teeth were in the control group. Changes in hypersensitivity levels were monitored after 6 weeks, using thermal, chemical and mechanical stimuli. At the end of 6 weeks, the test dentifrice was not significantly more effective than the control in decreasing dentinal hypersensitivity. Of the stimuli used, cold was the most effective in eliciting a hypersensitive response, followed by chemical stimulation and air. Heat and toothbrushing caused the least discomfort.

Fourier transform-pulsed field gradient and 1D NMR imaging studies of molecular and ionic diffusion in aqueous dispersions

The diffusion behavior of ions, e.g., MFP 2− (as sodium monofluorophosphate), Na +, and water molecules, in concentrated aqueous silica dispersions (pastes) has been examined by pulse field gradient (PFG)-spin echo (SE)-Fourier transform (FT) and simple one-dimensional magnetic resonance imaging (1D MRI) techniques, using a 300-MHz NMR spectrometer. Time-dependent 1D MRI concentration profiles for ions diffusing across ion-rich and ion-free paste boundaries are found to be in good agreement with those predicted from expressions based on standard Fickian laws of diffusion, using D self (self-diffusion coefficient) data determined by the FT-PFG-SE method. Accordingly, the D self value of 1 × 10 −6 cm 2 s −1 for MFP 2− ions is demonstrated to be representative of diffusion over realistic distances (0.5–1 cm), i.e., relevant to the transport of such species in practical systems, e.g., toothpaste. Initial evaluation of the resolution and multinuclear capabilities of the NMR methods is discussed via results on suitable models and solid-liquid “phantoms.”

Fluoride in plaque following use of dentifrices containing sodium monofluorophosphate.

Previous work showed that plaque fluoride increased with increasing NaF content of mouthwashes following daily use. The main aim of this study was to test whether a similar relationship was detectable after regular use of dentifrices containing amounts of sodium monofluorophosphate equivalent to 1000, 1500, and 2500 micrograms F/g. Plaque was collected from three groups, each consisting of approximately 80 children, who had each used one of the dentrifrices for one year. Plaque fluoride increased significantly with increasing Na2FPO3 content of the dentifrices. For the 1000-micrograms-F/g group, plaque fluoride also increased significantly with increasing frequency of dentifrice use, but did not correlate with amount of dentifrice applied per brushing. The inverse correlation observed between mean plaque fluoride concentrations and mean three-year caries increments suggests that oral fluoride measurements may prove valuable in estimating the likely anti-caries efficacy of fluoride-containing dental products.

Clinical studies of high-potency fluoride dentifrices: a review

A review of clinical studies indicates that increasing the fluoride content above 1,000 ppm in dentifrices containing sodium monofluorophosphate increases the mean caries reduction by approximately 12%. The results of studies testing high-potency mixed-fluoride dentifrices containing both sodium fluoride and sodium monofluorophosphate are less conclusive.

Interaction between chlorhexidine digluconate and sodium monofluorophosphate in vitro.

The aim of the present study was to investigate the compatibility of chlorhexidine digluconate and sodium monofluorophosphate since these agents are potential ingredients in future products in preventive dentistry. Varying combinations of chlorhexidine digluconate and sodium monofluorophosphate in water, covering the possible ranges of clinically relevant concentrations of both compounds, were made, incubated for 24 h and observed for precipitation of insoluble salts. The mixtures were analyzed for presence of free chlorhexidine and monofluorophosphate after incubation. The results showed that chlorhexidine digluconate and sodium monofluorophosphate are not compatible in clinically relevant concentrations. A chlorhexidine-monofluorophosphate salt of low solubility in water is presumably formed.

Effect of sodium fluoride, stannous fluoride, amine hydrofluoride and sodium monofluorophosphate on the formation of precipitates adhering to bovine enamel.

After in vitro treatment of surface enamel (bovine incisors) with aqueous solutions of various fluorides (pH 4.0, 5.0, 6.0) the elemental composition of the outermost zone was investigated by electron

Etching behaviour of bovine enamel after the formation of precipitates adhering to the surface.

Surface enamel was treated with various fluorides at pH 4.0, 5.0 and 6.0. After treatment, the kinetics of acid-induced surface removal were determined. Drastically reduced rates of surface etching were observed after treatments inducing precipitation of calcium fluoride. The effect was less pronounced after stannous fluoride treatment, which generated a complex tin precipitate of unknown chemical composition. The treatments with the nearly neutral solutions of sodium fluoride and sodium monofluorophosphate were without measurable effect on the acid susceptibility of surface enamel.

Effect of sodium lauryl sulfate on the deposition of alkali-soluble fluoride on enamel in vitro.

There are indications that sodium lauryl sulfate may reduce the cariostatic effect of fluoride when present together with sodium monofluorophosphate during topical application. The aim of the present study was to examine the in vitro deposition of alkali soluble fluoride on enamel during topical application with sodium fluoride in combination with sodium lauryl sulfate. It was found that increasing amounts of lauryl sulfate decreased the amount of alkali soluble fluoride deposited on the enamel. The amount of fluoride deposited from toothpaste supernatants was less than that from aqueous solutions of NaF with the same concentration of fluoride. Enamel pieces, pretreated with sodium lauryl sulfate showed a reduced deposition of alkali-soluble fluoride after incubation in a fluoride solution. It was also observed that the presence of lauryl sulfate increased the solubility of CaF2 in water.

Sodium fluoride promotes morphological transformation of Syrian hamster embryo cells

Sequential treatment of Syrian hamster embryo (SHE) cells with a chemical carcinogen followed by sodium fluoride (NaF) resulted in a higher yield of morphologically transformed cell colonies than treatment of the cells with carcinogen alone. For example, cells treated with benzo[a]pyrene (B[a]P; 3 micrograms/ml) for 3 days, then with NaF (25 micrograms/ml) for 4 days, exhibited a transformation frequency more than six times greater than that obtained by summing the transformation frequencies from cells treated with either B[a]P or NaF alone. This enhancement/promotion of cell transformation by NaF was only expressed after the cells had been pretreated with either direct-acting carcinogens or procarcinogens. Pretreatment of the cells with noncarcinogens or weakly-acting carcinogens or administration of NaF prior to treatment with the carcinogen failed to enhance the yield of transformation. Transformation was enhanced even when the NaF treatment was delayed for several days after the carcinogen treatment. However, the continued presence of NaF was necessary for maintenance of the increased level of transformation. Removal of NaF prior to termination of the assay resulted in a reversal of the transformed clonal morphologies to a normal phenotype such that the final yield of transformants was decreased, but was still greater than that observed after carcinogen treatment alone. A similar pattern for reversibility of the transformation enhancement also occurs for the widely recognized tumor promoter phorbol 12-myristate 13-acetate (PMA). Seven different SHE cell pools were tested for sensitivity to NaF promotion following carcinogen treatment. Although the response was heterogeneous, no carcinogen-treated cell pool was refractory to the NaF-induced enhancement. A second fluorocompound, sodium monofluorophosphate (NaMFP), was also found to enhance carcinogen-induced cell transformation in a manner resembling that of NaF.

Long-Term Exposure of Plaque to Zinc Citrate

The effect of 3 years’ continuous exposure to dentifrices containing different levels of sodium monofluorophosphate, with or without 0.5% zinc citrate, has been investigated on plaque growth inhibitio

Fluoride uptake in vivo by artificial caries lesions in root surface dentin from sodium monofluorophosphate dentifrices.

Fluoride uptake in vivo by artificial caries lesions in root surface dentin from sodium monofluorophosphate dentifrices.

Sodium monofluorophosphate degradation by oral streptococci, plaque and saliva.

Degradation of sodium monofluorophosphate (MFP) by selected oral streptococci, in vitro streptococcal plaque, natural dental plaque, and saliva, was investigated over the pH range 4–9, using a fluoride-ion-selective electrode. At 37 °C, optimum MFP hydrolysis occurred at approximately pH 5, but the level of hydrolysis activity varied depending on the streptococcal strain, plaque type, and incubation period. At the end of 23 h of incubation, the hydrolysis activity ranged from 0.23 μmol MFP decomposed/mg protein for Streptococcus sanguis plaque to 1.92 μmol MFP decomposed/mg protein for the Streptococcus salivarius cell suspension. On this basis, the hydrolysis activity of cell suspensions of S. salivarius ranked relatively the highest, followed by those of Streptococcus mitis and Streptococcus mutans, BHT. No significant differences were observed with the activities for MFP hydrolysis at both the 2- and 23-hour incubation periods between in vitro plaque and cell suspensions for S. mutans, 10449. Likewise, no significant difference in hydrolysis activity was generally observed between saliva from the rinsed and unrinsed mouth, however, the presence of 0.05% of cetylpyridinium chloride in saliva produced a significant change, reducing it to negligible levels compared to controls.